- Give NotebookEditorWidget its own ScopedContextKeyService
- Give the title control a way to get the context key service inside any editor
Fix #99318

Fixes #84033

Enables intellisene in the keybindings json editor for code actions and refactorings. Uses the new contribution point from #82718

* Converted another ~70 test files to strictNullChecks

These are the remaining test files that didn't require any changes to non-test file types. I'll send those in separately.

Most changes were automatic and small (`!`s).
The only non-trival change is that `extHostSearch.ts` needs an interface for its test data.

Again used [TypeStat](https://github.com/JoshuaKGoldberg/TypeStat) when possible per #65581. I'm happy to split this up into smaller PRs if you'd prefer!

* Added missing `!`s to `commands.test.ts`

This code pattern indicates that the type should be nullable

In these cases, the programmer has explicitly indicated that the type should be nullable

We set alwaysStrict so this directive is not needed